We compared the responses of two fleas, Xenopsylla dipodilli Parapulex chephrenis simultaneously exposed to the odours of their rodent hosts, Gerbillus dasyurus (specific host of X. dipodilli) and Acomys cahirinus (specific host of P. chephrenis). We hypothesized that, fleas are able to discriminate between host. species by using an odour cue and predicted that X. dipodilli and P. chephrenis would select an odour of an appropriate host Species. Xenopsylla dipodilli chose G. dasyurus significantly more often than A. cahirinus, whereas P. chephrenis chose A. cahirinus significantly more often than G. dasyurus. The ability, to select an appropriate host species did not differ significantly either between flea. species or between individuals of.,, different sex or age classes within flea species. No X. dipodilli, but 67 of 150 P. chephrenis, refused to choose a host. The latency to move in an experimental maze was. significantly shorter for X. dipodilli than P. chephrenis The flea species also differed in the time taken from the beginning of the movement to the choice of a host, with X. dipodilli being faster than P. chephrenis. Neither flea sex nor age affected this parameter in either species. Females of both flea species produced significantly more eggs when they fed on their specific host than when they fed on the other host species. (C) 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.